For those who are waiting for a review of the recent work on MSU temperature estimates, it’s coming. But it turns out to be a rather complex subject, with many papers to review and a lot of data to examine, so it’ll take a bit longer. In the meantime, the NASA GISS year-end estimates of monthly average temperature have been released, so let’s take a look. GISS provides monthly average temperature data from 1880 to the present for four areas: the land+sea (the globe), land, northern hemisphere land, and southern hemisphere land. The most oft-referenced data, which represent land and ocean for the entire planet, are the “globe” (land+sea) numbers.
I stated earlier that globally, 2007 was likely to end up being the 2nd-warmest year in the GISS record, surpassing 1998. It turns out that December 2007 was cooler than expected, so those two years ended in an exact tie; they’re in a “dead heat” for 2nd place. The hottest year in the GISS record is 2005; the five hottest years, in order, are:
| Place | Year | Average |
| 1st | 2005 | 0.62 |
| 2nd-3rd | 2007 (tie) | 0.57 |
| 2nd-3rd | 1998 (tie) | 0.57 |
| 4th | 2002 | 0.56 |
| 5th | 2003 | 0.55 |
Here’s the time series plot of annual average temperature, together with a smooth version (smoothed on a 5-year time scale):
Clearly there’s a lot of natural variation from year to year; the smoothed version eliminates much of the noise, making the long-term changes clearer. Another good way to reduce the noise is to take longer averages; here are 5-year averages (the last one is incomplete since we haven’t yet finished the 2005-2010 time slot), superimposed with the smoothed curve:
For land only, temperature has risen faster than the globe as a whole, due to the large thermal inertia of the oceans:
Even restricting only to land areas, the warming in the northern hemisphere has been greater still, and 2007 is by far the hottest year on record:
For the southern hemisphere the warming is quite a bit less, and the hottest year on record is not 2007 but 1998:
We can see the hemispheric contrast more clearly by plotting the two smoothed curves on the same graph:
From this we see that the slight cooling the planet’s land areas experienced from about 1940 to 1975 was pretty much restricted to the northern hemisphere; during that time, the southern hemisphere shows some wiggles but no sustained cooling. This agrees with the explanation that mid-century cooling was due to the increase of atmospheric aerosols from industrial activity. Man-made aerosols don’t stay in the atmosphere very long, so their climate impact is mainly regional (not “local,” but regional). The vast majority of mid-century industrial activity took place in the northern hemisphere, so most of the cooling effect of industrial aerosol production is confided to the northern hemisphere.
In a former post I showed that global average temperature from 1999 to the present (following the big el Nino year) was perfectly consistent with continued warming at a rate given by the trend calculated from 1975-1998 data. I also suggested in commentary that this is actually a legitimate way to inquire whether or not the trend has changed, and suggested using the 1975-2000 trend just to use round numbers. Here are the global annual averages from 1975 to the present, together with the trend line determined from monthly data from 1975 to 2000:
It’s abundantly evident that temperature since 2000 (following the regression interval) is perfectly consistent with the trend preceding it; in fact temperatures since 2000 have been a little warmer than expected from the preceding trend. We can see that even more clearly by computing the “residuals,” i.e., the difference between actual annual global average temperature and the value if it exactly followed the 1975-2000 trend:
This reveals, more clearly than any other way I’m aware of, just how wrong it is to claim that “global warming stopped in 1998.” Temperatures since then have been perfectly consistent with the preceding trend. In fact they really have been a little warmer, although the extra warmth post-2000 is not yet statistically significant.
I’m still waiting for HadCRU (the Hadley Centre for climate change research) and NCDC (the National Climate Data Center) to post their numbers for December 2007, completing the previous year’s reports. When they do, I’ll report the results.
101 responses so far ↓
Nigel Aimes // January 9, 2008 at 2:58 pm
Hi, this is a bit off-topic, but I’ve been reading this site for a while, and I know (or at least, I’m guessing) that your field is climate modelling.
I was wondering if you’d answer a question that I heard from a sceptic who claims to be very knowledgable about modelling and pooh-poohs the IPCC AR4.
I’ll just cut and paste what he said. He’s not a native English speaker, so please be patient with his sometimes clumsy expression:
As I have pointed out in my previous message, that the members of the public tend to follow the simplistic view of the IPCC, where in reality the simplistic models quoted in the IPCC are inefficient. The most inefficient of them all the the modeling of climate feedback systems. Again, if I had to make a claim, then I must point to the source which is shown below (see link), where this workshop was a NASA sponsored one, and they (about 30 of them) wanted to address the shortfall of modeling climate feedback systems. Shortfall means misleading, unless one had to persist in accepting that the model inefficiencies are not misleading. Such a scientist must be living in a dreamland if he/she had to keep using inefficient models.
http://grp.giss.nasa.gov/reports/feedback.workshop.report.html
This workshop was chaired by Dr. William Rossow of NASA , who had published his peer review work on the subject of non-linear coupled feed-back climate systems. I had made a few email exchanges with Dr. Rossow in the past, regarding his paper on the subject, in which I have read.
Dr. Rossow, was an IPCC author in 2001, but his report on feedback from 2001 is still unchanged in 2007, since there has been slow progress in the modeling of the most complex subject of them all in climate modeling domain. If someone is close to solving climate feedback systems, then we’re looking at getting closer to understanding the big question? Is human responsible or not?
[snip]
I have said in the past [...] that there is no single model in the whole IPCC report that nailed down CO2 as the driver (forcing) and this is fact and not perception, unless you can point me out to a model where CO2 is included as the driver function (forcing).
Does this guy have a point, or is he simply waving his hands to dazzle people and distract attention? Or (alternatively), is he cherry picking some uncertainties and exaggerating them?
I appreciate your help. Or lack of response; my feelings won’t be hurt ^^
[Response: I'm sorry to disappoint you, but climate modelling is not my field. I'm a mathematician specializing in the statistical analysis of time series.
The quote you give doesn't really seem to say anything substantive about climate modelling, except to make outlandish claims that it's utterly useless. As for the issue of feedback, another reader raised that issue a while ago, and I'm investigating the question but since it's *not* my field I have a lot of background work to do before commenting.
In the meantime, you could ask your question at RealClimate; some of the moderators there *are* experts in climate modelling.]
Nigel Aimes // January 9, 2008 at 3:00 pm
BTW, great post! But why oh why does the press insist on using the HadCRU rather than the GISS records?
Chris O'Neill // January 9, 2008 at 4:16 pm
It’s interesting to note that the 12 month period August 2006 to July 2007 had an average temperature only 0.007 (+/-ucertainty) deg C cooler than 2005. By chance, the hottest year around 2005 coincided with the 12 month period January 2005 to December 2005.
Horatio Algeranon // January 9, 2008 at 4:34 pm
Nevertheless, Global warming stopped in 1998. There’s really no debate.
Nigel Aimes // January 9, 2008 at 4:57 pm
Thanks for the response, I will ask at RC!
bob // January 9, 2008 at 6:08 pm
Not to load you up with additional work, but it may be useful to include the RSS MSU data in the annual review. RSS seems to bracket temperatures on the low end, with GISS at the high end.
Thanks for the post, as always very well done and informative.
Hank Roberts // January 9, 2008 at 7:07 pm
Tamino, you know William Connolley’s point about five year trends for climate data, I’m sure;
http://scienceblogs.com/stoat/2007/05/the_significance_of_5_year_tre.php#
Would it be convenient for you to show us which of the wiggles attain significance using the current red line for five year trends, and perhaps show ten year trends and their significance as well?
Your text is quite clear; even knowing how people see patterns that aren’t there, it’s easy to fixate on a wiggle!
John Mashey // January 9, 2008 at 7:53 pm
Nigel: suppose a class of models give good results. Practitioners don’t waste their time sitting around endlessly discussing what works, they talk about what doesn’t yet work as well as they’d like, waht they want to do next, etc.
If a non-expert sees these discussions, it can sound like “nothing works, we should throw these models”, even when the real answer is “We get very useful results, but we’d we’d like to increase precision, reduce uncertainties, etc.”
I used to go through this all the time when helping sell supercomputers to various kinds of modelers, in helping customers sort out wishes for perfection versus what was achievable, when.
Barton Paul Levenson // January 9, 2008 at 8:00 pm
Horatio Algeranon [sic] posts:
[[Nevertheless, Global warming stopped in 1998. There’s really no debate.]]
There is no debate because anyone capable of doing elementrary statistical math knows the claim is bogus. Global warming damn well did not stop in 1998, and only a statistical illiterate with an agenda would say that it had.
http://members.aol.com/bpl1960/Ball.html
[Response: I believe "Horatio Algeranon" was being sarcastic. If you follow his link, you'll see that what he stated is the first line of a humorous poem on the subject.]
Barton Paul Levenson // January 9, 2008 at 8:07 pm
Oops. My apologies to Mr. Algeranon.
-BPL
Barton Paul Levenson // January 9, 2008 at 8:09 pm
BTW, Tamino, how come the anomalies you list above don’t match the ones at the NASA GISS site? I just went there and they had 0.73 for 2007. Am I looking in the wrong column?
[Response: Maybe a different file. 0.73 is the anomaly in the file GLB.Ts.txt, which is for meteorological stations (i.e., land areas) only; the land+sea temperature file is GLB.Ts+SST.txt.
For those who are interested, the files can be found here.]
Horatio Algeranon // January 9, 2008 at 9:31 pm
Barton:
I may be sic, but I ain’t stupid. -:@~
And, as far as my agenda, you can find that here
No apology necessary. I have found that most people take mice way too seriously.
Regards.
Horatio
S2 // January 9, 2008 at 11:02 pm
I’ve just been playing with the GISS data, and it raises a question in my mind.
If plotting a trend from 1998 to 2006 really was “proof” that global warming stopped in 1998, then wouldn’t a trend from 1999 to 2007 be equal proof that it started again (with a vengeance) in 1999?
Oh wait - 1999 was a La Niña, so if I used this as my starting point I might be accused of cherry-picking.
A lie repeated is still a lie : Hot Topic · Global warming and the future of New Zealand // January 9, 2008 at 11:09 pm
[...] in the analysis of time series who blogs under the name Tamino at Open Mind, has just posted his latest analysis of the global average temperature data. It’s abundantly evident that temperature since 2000 [...]
Timothy Chase // January 10, 2008 at 12:28 am
I was looking at these figures a little earlier today, basically trying to compare the Hadley CRU combined global (land and ocean) with NASA GISS, trying to see how similar the stories are. I had remembered that warming in the past fifteen according to GISS was much greater than in the brief period of warming up to 1944, but when trying to do the same calculations for people who are probably more familiar with Hadley, I had come up with:
1917-1944 0.177 C Decade CRU (global)
1978-2006 0.178 C Decade CRU (global)
*2007 not available for Hadley yet
… but that was specifically selecting the period of warming (both ends) according to CRU.
I got the following for CRU and GISS, 30 year spans….
CRU Land and Ocean
1914-1944 0.151 C/Decade
1977-2006 0.173 C/Decade
GISS Land and Ocean
1914-1944 0.104 C/decade
1977-2007 0.193 C/decade
Obviously the latter thirty years is experiencing greater warming. Then split the thirty years into two periods…
CRU Land and Ocean
1977-1992 0.110 C/Decade
1992-2006 0.278 C/Decade
GISS Land and Ocean
1977-1992 0.132 C/decade
1992-2007 0.350 C/decade
John Mashey // January 10, 2008 at 7:22 am
A great quote:
I was at dinner tonite with some academic friends, and in the topic “What makes for an educated person” I expressed the wish that it would be nice if everyone at least understood error bars and how to look at graphs critically. Another person recounted something he’d said in a talk:
“Ideologies don’t have error bars.”
Bruno De Wolf // January 10, 2008 at 9:01 am
Note that the claim ‘earth didn’t warm since 1998′ is not necessarily incompatible with the claim that temperatures are ‘perfectly consistent with continued warming at a rate given by the trend calculated from 1975-1998 data’.
For the sake of the example, look at the following table:
Year - temperature
1000 - 10C
1100 - 11C
1200 - 12C
…
1800 - 19C
1900 - 19C
2000 - 19C
Within the natural fluctuations, the 1800 - 2000 temperatures are in line with a warming trend of 1C / century, but you can also say that there is no warming between 1800 and 2000.
The crucial factor is of course ’scale’. Why only look at a 30 year scale (warming = 1,7C) and not at a 10 year (warming = 0C) or a 100 year scale (warming = 0,7C)?
Adam // January 10, 2008 at 10:27 am
Preliminary Hadley 2007 result can be found here:
http://www.metoffice.gov.uk/corporate/pressoffice/2007/pr20071213.html
I guess they were reasonably sure of how much it was likely to (not) change in the last 18 days. Though the timing was obviously based on, or at least influenced by, Bali.
John Finn // January 10, 2008 at 1:09 pm
“Obviously the latter thirty years is experiencing greater warming. Then split the thirty years into two periods…
CRU Land and Ocean
1977-1992 0.110 C/Decade
1992-2006 0.278 C/Decade
GISS Land and Ocean
1977-1992 0.132 C/decade
1992-2007 0.350 C/decade”
Why not split it into 3 10-year periods? particularly as 1992 begins the sharp 2-3 year cooling period caused by Pinatubo.
P. Lewis // January 10, 2008 at 4:06 pm
Because 30 years is the acknowledged minimum period (as per WMO definition) over which climatology data (temperature anyway) need to be assessed to take account of weather noise.
Maribo // January 10, 2008 at 5:12 pm
Tamino - Great post as always. One point. You say “from this we see that the slight cooling the planet’s land areas experienced from about 1940 to 1975 was pretty much restricted to the northern hemisphere. This agrees with the explanation that mid-century cooling was due to the increase of atmospheric aerosols from industrial activity”
That may be right, but the evidence you give is purely correlative. There are a couple other strong possible drivers for the cooling period in the 20th century. First, there is some observational and model evidence for the AMO, a 60-80 year oscillation in N Atlantic SSTs, which drives northern hemisphere climate. Second, the huge increase in irrigated area on the planet occurred during that period and some studies suggest it could have led to some evaporative cooling (again, in the NH, since that’s where most of the land and most of the irrigation is).
I’m not saying that aerosols are not the major driver — but we don’t know that for certain.
fred // January 10, 2008 at 5:35 pm
They are interesting graphs, not unfamiliar, but I do find them a little frustrating, because its so unclear what they prove, absent some parameter on what it takes to be outside the bounds of natural variation. Yes, you can see that the recent rise in temps is more impressive and different in shape than the earlier ones in the period for which there is data. But…what does this entitle us to conclude?
To look at graphs like this is to be convinced that the proxy record, if we could get a convincing account of it, really has something to teach us.
steven mosher // January 10, 2008 at 6:08 pm
you guys should visit traverse city michigan
Boris // January 10, 2008 at 6:23 pm
“For those who are waiting for a review of the recent work on MSU temperature estimates, it’s coming. But it turns out to be a rather complex subject, with many papers to review and a lot of data to examine”
Not to add to the complexity, but a comment on James Annan’s blog suggests that the UAH team think the RSS values have a recent cool bias. Has anyone else heard anything about this?
Here’s the comment
Mike B // January 10, 2008 at 6:25 pm
“Second, the huge increase in irrigated area on the planet occurred during that period and some studies suggest it could have led to some evaporative cooling (again, in the NH, since that’s where most of the land and most of the irrigation is). ”
Would this imply that the increase in evaportated water in the Northern Hemisphere resulted in increased rainfall in the Southern Hemisphere?
I say that because I would assume that since the life cycle of water vapor is very short, wouldn’t the resulting condensation return that energy mostly in the Northern Hemisphere as well?
nanny_govt_sucks // January 10, 2008 at 6:25 pm
Where do we see empirical evidence that industrial atmospheric aerosols (non-stratospheric) actually cause cooling? As I understand it, natural aerosols are bright and can cause cooling, but man-made aerosols like black carbon are dark and can cause warming (more http://www.unisci.com/stories/20013/0817013.htm). Additionally, we see warming in places where man-made aerosol production is high over the last 20 years or so, even at USA latitudes (see Northern China in fig d.: http://www.grida.no/climate/ipcc_tar/wg1/fig2-9.htm).
Hank Roberts // January 10, 2008 at 7:33 pm
You’re understanding different things as the same, and similar things as different, or your wording confuses them.
The result will be confusion, though I can’t tell if it’s your confusion, or your wording that would confuse a naive reader. I realize this usually becomes whack-a-mole and won’t go beyond one reply to you on this one.
Here’s what you’re conflating:
Natural soot is black. So is soot from human activity. Natural sulfate is reflective. So is sulfate from fossil fuel.
Both change over time after emission and both change other things depending on where they go over time.
http://eobglossary.gsfc.nasa.gov/Library/glossary.php3?xref=sulfate%20aerosol
http://eobglossary.gsfc.nasa.gov/Study/GISSTemperature/Images/greenland_sulfur.gif
Timothy Chase // January 10, 2008 at 8:13 pm
Re John Finn, P. Lewis
The definition of a climate doesn’t really say much about how short a period of time is required to identify a change in climate. If you check out:
The significance of 5 year trends
Posted: May 17, 2007 4:02 PM, by William M. Connolley
http://scienceblogs.com/stoat/2007/05/the_significance_of_5_year_tre.php
… 5 year trends are basically all noise (red noise - due to autocorrelation), but 15 year trends are mostly signal.
The central reason for the noise has to do with the major climate oscillations.
A good place to look for some detailed information on them is:
UN Atlas of the Oceans: Major Oscillations
http://www.oceansatlas.org/servlet/CDSServlet?status=ND0xMjczMyY2PWVuJjMzPSomMzc9a29z
For example, during the La Nina part of the El Nino-Southern Oscillation, a pool of warm water builds up in the ocean with only a small interface between it and the atmosphere, then at some point this interface expands and the pool spreads out along the surface, at which point we enter the El Nino stage. This causes the atmosphere to heat up. But once the additional heat content is lost from the ocean, its back to the La Nina.
Oscillations along these lines are what make short-term climate prediction more difficult. However, currently we are getting better at mapping the heat content of the oceans and actually beginning to incorporate this data into the models - with different groups trying to make climate predictions on a decadal scale and Hadley’s DePre Sys being the most well known attempts along these lines.
*
Incidentally, such oscillations (”climate modes”) may become synchronized — and it appears that when they do so this can mark the transition from an old climate regime to a new one:
“Analysis of the climate modes as a network of interacting nodes revealed that in the twentieth century, the modes synchronized in the 1910s, 1920s, 1930s, 1950s and 1970s. In those cases where the coupling strength between the modes increased before the synchronization broke up, changes in global temperatures and the strength and frequency of El Niño events ensued. This occurred in 1912/1913, when global temperatures increased and El Niño events became stronger, in the early 1940s, resulting in cooling temperatures and weaker El Niño phenomena, and in the late 1970s when temperatures again warmed and El Niño effects grew.”
Oct 22, 2007
Interacting climate modes cause climate shifts
http://environmentalresearchweb.org/cws/article/research/31546
Technical Article:
Tsonis et al, A new dynamical mechanism for major climate shifts
Geophysical Research Letters, Vol. 34, L13705, doi:10.1029/2007GL030288, 2007
Barton Paul Levenson // January 10, 2008 at 8:22 pm
nanny writes:
[[Where do we see empirical evidence that industrial atmospheric aerosols (non-stratospheric) actually cause cooling?]]
We’ve been over this before in other threads. Your pattern appears to be to raise some denialist argument, have your ass handed to you, wait a while, then raise the same damn argument in another thread. It gets annoying after a while.
Timothy Chase // January 10, 2008 at 9:27 pm
Barton Paul Levenson responded to Nanny, “We’ve been over this before in other threads. Your pattern appears to be to raise some denialist argument, have your ass handed to you, wait a while, then raise the same damn argument in another thread. It gets annoying after a while.”
I saw that sort of tactic all the time while debating creationists for three years.
(Quick aside: this isn’t the only similarity. With the guys over on Climate Audit, you will see claims to the effect that climatologists have forgotten the second law of thermodynamics — just as creationists claim that evolutionary biologists have done so.)
Anyway, what I have done in the past with such people is link to where they made the same argument before and include a little quote, then link to the earlier response and include a little quote from days, weeks or months before. Later when they do the same thing again you can link to the places where you have made such links. That way you show that not only is there an answer but that they are being dishonest when they bring up the same invalid argument again.
I know: its a little more work. But a large part of their strategy seems to be the attempt to wear you down, and to the extent that they get you to respond with anger but very little substance, they figure that they are succeeding — making you look bad in the eyes of someone who has just wondered in.
*
Oh, and as for creationists in the denier’s camp, I ran into a major player just recently in a ten-day exchange at The Register (UK). “Dr.” Stephen Jones of Creation Ministries, formerly a part of Answers in Genesis. He didn’t participate much, but he did get the last word just before the thread was closed.
Please see:
Comments on ‘Cloudy outlook for climate models’
http://www.theregister.co.uk/2007/12/27/anton_wylie_climate_models/comments/
The deniers were pretty nasty at first. And one who at least pretended to be civil required a fair amount of repetition - which was more difficult due to the absence of hyperlinks.
Ian // January 10, 2008 at 11:15 pm
Tim, that was a virtuoso effort of patience and scholarship! It was also nice to see signs that you were convincing some readers…
P. Lewis // January 10, 2008 at 11:25 pm
Re T. Chase
I perhaps could have phrased it slightly better. The bottom line is that if the results are (properly) statistically significant then it doesn’t matter what period you calculate on really. Anyway: climate, definition, and climate normals, the nitty gritty and history.
tamino // January 10, 2008 at 11:36 pm
I agree Tim, your efforts on that discussion were laudable. And your patience is far greater than my own.
Timothy Chase // January 11, 2008 at 12:39 am
Regarding the debate on the Register…
Ian wrote:
Glad you like!
Not sure that it was convincing any of those who participated, although it required them to shift positions and form. As near as I can tell, the positions they take and even the level of politeness is more a matter of debate strategy than concern for the truth. The initial rudeness, for example is meant to intimidate those who might otherwise openly disagree with them into not responding.
Depending upon how you respond to them, your politeness can make their impoliteness look bad, and after a bit they will tend to realize this. When they actually have to at least pretend to be civil, that works to your advantage as it shifts the focus from ad hominem to substantive issues.
However, I did get a couple of emails from one lurker out of North Ireland who was quite impressed. And I am sure there were others.
In the retail industry they say that for every customer that complains there are nine others who never return. In this case I figure that for every lurker that writes an appreciative note, there are at least nine others who picked up alot. Besides, the discussion made available certain resources for those who might participate in later debates.
tamino wrote:
I enjoyed it. As for patience and the ability to recognize online debate tactics, you learn that — particularly when dealing with certain creationists — such as a certain Laurie A. of Australia. More than half a year in the same forum.
nanny_govt_sucks // January 11, 2008 at 7:18 am
Yes, aerosols have been discussed, but I don’t think this question has been answered. If I’m wrong, please provide a link.
Marion Delgado // January 11, 2008 at 7:18 am
I went through the soot issue with 5 different trolls. Every one of them exhibited the behavior Barton Paul Levinson cites.
We don’t have a Con-Troll group .. oh wait, that’s all we have! okay, the null hypothesis (the hypothesis that they are nulls) is confirmed.
nanny_govt_sucks // January 11, 2008 at 7:27 am
Hank, from your first link:
“Recent theory suggests that sulfate aerosols may lower the Earth’s temperature by reflecting away solar radiation (negative radiative forcing).”
Sounds good in theory, but what I’m looking for is the empirical evidence to support the theory.
fred // January 11, 2008 at 8:17 am
Timothy, you suggest above that scepticism about AGW is in the same category as creationism and that CA is in this category.
This sort of debating tactic is counter productive. Anyone who reads CA knows that McIntyre is not in this category at all. Anyone who like me is picking their way through the evidence on AGW and making up their own minds will find the conflation simply insulting.
It is getting to the point where one of the intuitive reasons for scepticism about AGW is the fanaticism and intolerance and name calling of AGW proponents. I am not yet convinced, may never be, and calling me names is not going to convince me. What may at some point convince me is evidence and rational argument.
Right now I am looking again at Tamino’s chart and asking myself, yes, we see that warming since 1975 is faster and larger and higher than in the period up to 1940, at least in the NH. Now, what exactly does this prove? How unusual are such warming periods in long term climate history? What’s the evidence?
I would also say that your particular horror of creationism is misplaced. To swallow Christianity as a whole and strain at creationism - well, its the proverbial gnat. But you will not be, presumably, dismissing all Christians who have opinions on the climate simply because of their religion?
John Finn // January 11, 2008 at 12:27 pm
In his article, Tamino says
“It turns out that December 2007 was cooler than expected ”
Why “cooler than expected”? The current La Nina is now having an effect on global temperatures (the lag is normally about 6 months). Conditions in the Pacific are now similar to what they were circa 1999. The years 2001-2007 were dominated by El Nino
or El Nino-type conditions.
Later he writes
“This agrees with the explanation that mid-century cooling was due to the increase of atmospheric aerosols from industrial activity. ”
Not Really! In the nest sentence, Tamino says
“Man-made aerosols don’t stay in the atmosphere very long, so their climate impact is mainly regional (not “local,” but regional).”
Exactly. Central England, Western Europe and parts of the US should have exerienced the greatest cooling. They didn’t. The cooling trends seen in Greenland (well away from industrial activity) were higher than the indiustrialised regions.
“The vast majority of mid-century industrial activity took place in the northern hemisphere, so most of the cooling effect of industrial aerosol production is confined to the northern hemisphere.”
The whole of the NH is a bit more than “regional”. The post-war industrialised regions were less than 10% of the NH. Aerosols are a fudge factor. If they were the real reason for cooling it would be easy enough to demonstrate it. As it is the IPCC quotes uncertainties of around 1 w/m2 for the aerosol effect.
Finally, industrial processes were producing aerosols during the1920s and 1930s when the world was warming. Then all of a sudden enough aerosols (*EVERY year - NOT cumulative) were being produced to not only stop the warming (whatever the cause) - but reverse it. OK industrial production did increase after the war but so, presumably, did CO2 emissions.
*The aerosol production in 1945 alone, for example, would need to be of such magnitude that ALL warming factors are negated. The 1945 aerosols last only a few months in the atmosphere - so the 1946 aerosols would have to replace and add to the 1945 aerosols - and the 1947 aerosols would have to replace and add to the 1946 aerosols and so on ……….
The NH is naturally more variable than the SH because of the differing ratios of Land/Ocean areas.
Barton Paul Levenson // January 11, 2008 at 3:42 pm
John Finn writes:
[[ Aerosols are a fudge factor. If they were the real reason for cooling it would be easy enough to demonstrate it. ]]
Okay, here’s a demonstration. Under a lot of circumstances, the decrease in intensity of a beam of light can be described by the Beer-Lambert-Bouguer law:
dI = I k ρ ds
where I is the intensity, k the extinction coefficient, ρ the density, and ds the path length. Now, extinction happens two main ways:
By absorption by material in the path of the beam.
By scattering by material in the path of the beam.
For the latter, some aerosols are very efficient scatterers of sunlight. That’s why clouds cool the Earth (they also warm it, but that’s another story) — they reflect sunlight back out to space.
Now, consider the components of the extinction coefficient:
ke = ka + ks
where ka is the absorption coefficient and ks the scattering coefficient. We now introduce the single scattering albedo:
ω = ks / (ka + ks) = ks / ke
When ω is high, scattering is the dominant effect. Consideration of the “phase integral” can be used to find yet another factor, the linear scattering fraction f. This is just the fraction scattered forward rather than backward. If f = 0.5 a photon has a 50-50 chance of going down or up.
For sunlight, when f 0.5, more sunlight is scattered than absorbed, so the scattering layer doesn’t heat up very much, either. Net result: a cooler climate system.
Sulfate aerosols in the stratosphere tend to cool. Rock dust in the Martian troposphere tends to warm. It all depends on ω and f.
Your homework assignment: Look up climate models and see what values of ω and f they assign to stratospheric aerosols. See why they derive the factors they do.
Barton Paul Levenson // January 11, 2008 at 3:49 pm
Oops. Forgot the less-than sign would be interpreted as an HTML tag. Substitute “f < 0.5″ in the 12th paragraph above.
Tamino, is it possible to add a preview feature to this blog, or would it be too much of a hassle? Just wondering…
Barton Paul Levenson // January 11, 2008 at 3:52 pm
Come to think of it, that whole paragraph was mangled. Should have read, for high ω and f < 0.5 in a high-altitude aerosol,
less sunlight reaches the ground, and
more gets reflected out of the atmosphere than heats the aerosol layer.
Mr. Finn — Industrial production was much higher in the ’40s than in the ’20s and ’30s. World War II was going on. See any economics textbook with a good time series for GDP or industrial production in the back.
guthrie // January 11, 2008 at 3:53 pm
Fred, I’m afraid that we shall have to agree to disagree on climate audit and MacIntyre and their similarities or not to creationism.
And as for you lot in the peanut gallery, you know who you are, don’t make any comments on this particular topic, ok?
However Fred, you yourself are not showing real signs of it so far as I can see, so please, carry on.
Heretic // January 11, 2008 at 5:31 pm
Fred, the worst name calling I’ve seen so far (some of which directed at me on other blogs) was from “skeptics.” For a while, the Scientific American blog had regulars who, interestingly, were aggressively attacking both AGW and the theory of evolution.
As for CA, the fundamental mission of it is to very carefully nitpick and cast doubt on the science pointing to conclusions disliked by SteMac. As a lurker there, I have seen great complacency directed to “evidence” pointing to the better liked conclusions. In addition, the name calling and fraud accusations I’ve seen on CA were worse than any other site with true scientific pretentions (well, almost, Deltoid is pretty bad, lack of moderation I guess). In short, my experience disagrees with your perception.
luminous beauty // January 11, 2008 at 6:55 pm
fred,
“It is getting to the point where one of the intuitive reasons for scepticism about AGW is the fanaticism and intolerance and name calling of AGW proponents.”
Does this not equally apply to AGW ’skeptics’?
Though you wish, by mere assertion, to separate McIntyre’s skepticism from ‘creationist’ arguments against evolution, it is readily apparent that the same type of arguments are employed by both, i.e. the ‘world is too complex for us to understand’, and ‘there might be unknown unknowns that might possibly completely negate well supported theoretical understanding’. Add to this the tactic of wearing one’s opponent down by re-asserting, ad infinitum, claims that have been repeatedly and exhaustively addressed without any apparent awareness or understanding that they have been addressed.
It is enough to make a grown man cry. It is only human that one should sometimes become somewhat frustrated with such persistent ignorance and let a mean word slip.
Marion Delgado // January 11, 2008 at 9:33 pm
Heretic, I have to defend Deltoid, it’s not just lack of moderation, it’s that that is where both the vilest and most prolific denialist trolls of all stripes congregate - probably because Tim addresses so many kinds of denialism, and probably because the denialism blog is less well-known and more moderated in terms of who can comment.
Of all the sites i visit on the Internets, Deltoid is the one where my Greasemonkey killfile benefits me the most. It’s usually impossible to follow a discussion there, because no matter how fast you respond to an intelligent question, there will be about 10-15 posts by shrieking weasels in between.
A lot of tim’s posts i just read, and ignore the comments entirely.
Timothy Chase // January 11, 2008 at 10:28 pm
Fred, I wasn’t debating anyone. I was being candid with friends — and granting myself a great deal more latitude in this than I typically do.
What I see often are people who place politics and ideology before science. In some cases what drives them a form of religious fundamentalism which becomes quite evident in their debating style and even the specific arguments which they employ — regardless of whether they are arguing against evolutionary biology or climatology.
Young earth creationists are especially notorious for this. And in some cases these are the same people. In fact, I ran into a “Dr.” Stephen Jones of Creation Ministries (formerly of Answers in Genesis) in my last debate.
If he had his people there, it might explain some of the fanaticism that I saw on the other side, especially early on in terms of the preemtive name-calling and intimidation.
Among the more active young earth creationists, everything will often reduce to a religious war of some kind, and science (to the extent that it contradicts how they choose to interpret the Bible) is often seen as some great conspiracy. I don’t think that’s good for science, religion or society, and I should think that despite whatever other differences may exist, this is a point that you, McIntyre and I could all agree on.
P. Lewis // January 12, 2008 at 12:51 am
BPL
I preview at any blog that allows previewing (RC, Rabett Run, …). Just don’t push the publish button there by mistake.
And you could do the maths in LaTeX here, unless it’s not been activated in comments (or preview). This should test it out:
[tex]k_{\mathrm{e}}=k_{\mathrm{a}}=k_{\mathrm{s}}[/tex]
[Response: There's no preview function here; this is a free wordpress acct. and I don't seem to have one among the options. It seems that LaTeX works in posts but not for comments.]
P. Lewis // January 12, 2008 at 1:30 am
Bu**er!
One final try (since I’ve seen it used in comments in other WordPress blogs — possibly only after moderation, which suggested some manual intervention necessary). Anyway, final try:
$k_{\mathrm{e}}=k_{\mathrm{a}}=k_{\mathrm{s}}$
and then I’ll give up. :-( (-:
P. Lewis // January 12, 2008 at 1:31 am
Argh! Should have had latex after the initial $. Where’s the preview ;-)
BTW Excellent blog. Long may it continue.
EliRabett // January 12, 2008 at 4:50 am
Sulfate aerosol are pretty much what you get in volcanic eruptions and yes they cool.
Heretic // January 12, 2008 at 5:44 am
OK Marion, I’ll take your word for it, I just don’t like the general tone there.
Timothy Chase // January 12, 2008 at 8:45 pm
Tamino wrote in the essay:
John Finn responded:
He said “regional,” not local. And when you are thinking “aerosols” you have to be thinking “downwind.” Parts of Greenland are downwind of the United States and Canada, and other parts are downwind of Europe and Asia. And as a matter of fact, we are able to estimate North American sulfate and nitrate emissions for the earlier part of the twentieth century based on ice core samples from appropriate sites in Greenland.
Please see:
You also appear to be ignoring polar amplification where the extent of warming or cooling will be dependent upon the latitude — with higher latitudes experiencing more warming or cooling.
John Finn wrote:
Once again you seem to be assuming that the effects of atmospheric circulation. And there is no “fudge factor” associated with sulfates or nitrates. There is uncertainty, but they are estimated independently of the climate models based upon industrial output, air samples and ice core samples. Given their optical properties and distribution in the atmosphere we are able to estimate their effects. We are also able to do this in the case of sulfates due to volcanic eruptions when their concentrations rise well above the background noise and general trend of warming — which provides us with an additional means of testing models.
John Finn wrote:
Yes, emissions of CO2 would have increased at the same time and in roughly the same proportion, but the forcing due to carbon dioxide is the result of what has accumulated in the the atmosphere over decades. And as you are aware, aerosols in the troposphere tend to wash out with the rain.
All things being equal, a large drop in industrial production will mean that the aerosols get washed out of the atmosphere and we are left with the cummulative effects of carbon dioxide from previous decades. Given this, a more pronounced warming during the 1930s makes sense.
As industrial production ramped up, while both greenhouse gases and reflective aerosols will increase, as a percentage of the atmospheric concentrations, aerosols will climb much faster. Carbon dioxide has a far longer residence time, with much of its concentration being due to the past several decades of industrialization. Thus a recent increase in industrial production will have far less of an effect upon its total concentration.
John Finn wrote:
Yes, for a total of six years we would have to experience more or less continuous economic growth in order to explain the global cooling trend we saw from 1945 to 1951. And I believe we did. Something about a post-war boom, if I remember my history correctly…
nanny_govt_sucks // January 12, 2008 at 9:43 pm
Eli, how about empirical evidence that industrial atmospheric aerosols (non-stratospheric) cause cooling? Do you know of any?
P. Lewis // January 13, 2008 at 12:45 am
Source:
No doubt you could find the studies in the peer-reviewed literature, if one tried.
EliRabett // January 13, 2008 at 3:17 am
SO2 aerosols don’t have little signs saying who their parents were.
Hank Roberts // January 13, 2008 at 4:36 am
You have to spy on them from above to ascertain their origins:
Land
http://earthobservatory.nasa.gov/Study/UrbanRain/urbanrain3.html
Ship tracks
http://earthobservatory.nasa.gov/Library/CALIPSO/Images/ship_track.jpg
henry // January 13, 2008 at 11:23 am
EliRabett said:
“SO2 aerosols don’t have little signs saying who their parents were.”
But couldn’t increased patterns of rain (caused by increased pollution of sulfate aerosols) be traced back “upwind” to their most likely source?
Also, do the CO2 monitoring stations also have set-ups to track SO2? They might be able to map localized concentrations.
john Finn // January 13, 2008 at 2:54 pm
Boris (10th Jan) says
“Not to add to the complexity, but a comment on James Annan’s blog suggests that the UAH team think the RSS values have a recent cool bias. Has anyone else heard anything about this? “
I’ve heard UAH believe their own data has a warm bias over the past 2 years. The following comments can be found on the UAH site:
Update 19 Dec 2007
As noted below, the diurnal drift of NOAA-15 is becoming more obvious. We
are still working on a correction scheme to remove this spurious warming
effect. Through comparison with other AMSUs, the warming drift by
Oct and Nov is on the order of 0.2 C (i.e. the values of v5.2 are too
warm for TLT by that amount.) This has been a long ordeal because we
want to create a correction that will stand the test of time.
Update 10 Sep 2007 *****************************
Note that NOAA-15 is drifting backward into a warmer part of the diurnal
cycle which will induce a spurious warming in the values for the last couple of years in LT and MT (see 12 July 2007). Information from Carl Mears indicates
the spurious warming in our LT and MT global anomalies will be about +0.08
and +0.04 respectively by mid 2007 (for the anomalies). Because we have not solved all of the peculiarities with NOAA-15 (especially channel 6) our intent to generate a multi-channel AMSU replacement for old MSU LT and MT is still on hold. Be advised that the LT and MT products are a little too warm in the past couple of years, but less than 0.1K
john Finn // January 13, 2008 at 3:04 pm
Dear All
You can arm-wave all you want . Industrial aersosols are an unkown fudge factor.
I live right in the heart of the most intensely industrialised regions in the NH. The city I live in was called boom city. In the post-war years it manufactured everything from cars to tractors to aircraft to motorcycles, tyres, plastics etc etc. Just down the road there is a region called the “black country” an area which was littered with ironworks, foundries and yet more factories.
And yet Greenland experienced about 3 times the cooling than this entire region experienced. All because Greenland is downwind of the US and Europe.
Have a day off, TC, and just think avbout it a bit.
P. Lewis // January 13, 2008 at 3:45 pm
john Finn said:
On following Boris’s link to James Annan’s blog (and reading through the OP and the link(s) and comments) you would have read the following comments from Chip Knappenberger (CK).
On 8th January 2008 CK wrote:
On 10th January 2008 CK wrote:
P. Lewis // January 13, 2008 at 7:07 pm
Re jF
Who’s waving arms?
Just a thought, but I wonder why arctic peoples carry the very high levels of toxics they do (considering their lack of industry) and why the pristine arctic is not that pristine.
PCBs
haze, etc.
…
Now far be it from me to suggest someone takes time out to ponder, … happy reading!
P. Lewis // January 13, 2008 at 7:21 pm
Re jF again.
Somehow the links in my previous message seem to have got mangled (though it could be due to not showing properly because the message is in moderation).
Anyway, here they are again just in case:
PCBs
haze, etc.
EliRabett // January 13, 2008 at 7:22 pm
One of the tricks the TOMS (ozone monitor) plays is that it can also track SO2
http://www.osei.noaa.gov/TOMS/
John Finn is confusing black carbon with SO2 aerosols.
P. Lewis // January 13, 2008 at 7:49 pm
Re jF and aerosols and Greenland again. With just a little more digging I found one secondary ref and a reprint from an IGACtivities Newsletter.
First there’s this reference to Greenland ice cores showing a 2- to 3-fold increase in sulphate (and nitrate) deposition in the last ~100 years (near bottom of page; the reference is to Elsworth 1984)
And then there’s the IGACtivities Newsletter reprint; an excellent, if dated, source.
P. Lewis // January 13, 2008 at 11:25 pm
To echo slightly EliRabett, the Black Country got its name principally on account of particulates, namely soot, ash, silicates, aluminates, …, going up the smoke stacks and settling and precipitating out.
Sure, there were also aerosol sulphates, VOCs, etc. amongst the pollution, but as EliRabett alludes to, black carbon has different properties to sulphate aerosols, vis-a-vis its effect in climate change, as this BBC article reports.
Timothy Chase // January 13, 2008 at 11:34 pm
Temperatures in Greenland… and Antarctica
john Finn wrote:
Actually I said that aerosols reach Greenland in sufficient quantities that we are able to use ice core samples as proxies for air pollution from North America in the southern part of Greenland and for Eurasia. As such, northern hemisphere atmospheric circulation is clearly taking those aerosols far enough that Greenland is recieving them — which strongly suggests that it is subject to some of the direct effect of these aerosols and undoubtedly to a much greater degree the indirect effects of such aerosols insofar as they form the nuclei for cloud formation. And given the fact that they are distributed by atmospheric circulation rather than simply staying put over the country of origin, their effect should be wide enough to affect much of the northern hemisphere. Likewise, with the northern hemisphere so affected, polar amplification will become an issue for both warming and cooling trends.
Please see:
Real Climate: Polar Amplification
http://www.realclimate.org/index.php?p=234
As such, I was attributing the early twentieth century cooling in Greenland both to aerosols (in terms of both their direct and indirect effects) and polar amplification of this cooling trend.
Of course Greenland is a bit of a side issue as we are discussing polar amplification in global warming, the effects or aerosols and the like. But as we have focused on temperatures in Greenland, I thought I would go into it in a little more detail which gives me the chance to show off some of the resources off that are available on the web which may be of more general interest…
Station Records
If you wish to investigate temperature trends for stations in Greenland, or for that matter, anywhere else in the world, a good way to begin would be to get Google Earth at:
Google Earth
http://earth.google.com
… then get the kml file at:
Global Temperature Station Data in Google Earth
http://dev.edgcm.columbia.edu/wiki/StationData
Looking at a map of the Greenland temperature stations, the first thing one should notice is that all of the temperature stations are fairly close to the coasts. As such they will be strongly affected by changes in local sea surface temperatures. Local sea surface temperatures will be strongly affected by changes in sea currents. As such, one should expect and will find that there is a fair spread of behavior between various stations.
For example, SDR. Stromfjuo (67.0 N, 50.8 W) shows a climbing trend from 1949 to 1970 — the length of the station record, although one might argue about 1967-1970 over which the temperature is “falling.” Then again, a “five year trend” means very little even when applied to global temperatures as nearly all of what one is seeing is due to natural variability — climate modes, which in this area would most likely be dominated by the North Atlantic Oscillation, but will of course also be affected by the El Nino-Southern Oscillation, which is of course both regional and global in its effects.
http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=431042310000&data_set=1&num_neighbors=1
With Godthab Nuuk, the second farther station to the south but along the west coast, one sees a great deal of variability as one is getting close to the southern tip of Greenland. For the years 1945-1954 the average annual temperatures (C) are -1.53, 0.03, 0.98, -0.70, -2.53, -1.15, -0.71, -0.65, -0.36, -1.15. There is a steep drop from 1947-1949, but nearly half of this is recovered in 1950 and somewhat more in the next few years that followed. One might argue, however, that a cooling trend began as early as the onset of the Great Depression, with temperatures reaching 0.92 C but generally declining throughout the rest of the twentieth century until 1983 with an annual average temperature of -4.34 C, but not really beginning its steep, more recent climb until 1993 (when the temperature was -3.93 C but climbed to -2.44 C the succeeding year.
http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=431042500000&data_set=1&num_neighbors=1
With Ivigtut at the southern most tip of Greenland (available in Google Earth Global Temperature Station data by GISS), the temperature records extend from 1880 to 1966. In its case, one might try and break up its record into distinct periods of warming, lack of warming, cooling, etc., but one could also argue that it has experienced a consistent warming trend throughout its entire record — which given the data and natural variability would seem to be the simplest interpretation.
Looking at the station Nord Ads farthest to the north but somewhat sheltered by a bay, the data is so short and sparse one can say little more than that there was an apparent cooling trend from perhaps 1953 to 1971 but a warming trend when looking at the whole from 1953 to 1987. Thul Op and Dundas Radio are likewise short.
Upernavik is relatively far to the north at 72.8 N, which would make it more likely to be affected by Europe but is along the west coast. In its case, I would almost be inclined to divide its temperature record into regimes — although there is a rather rapid descent in the late nineteen forties — consistent with the onset of North Hemisphere cooling and polar amplification. But there appears to be a warming trend beginning in the early 1970s extending into the mid nineteen eighties, where the temperature record ends.
http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=431042100000&data_set=1&num_neighbors=1
For other stations in Greenland without the aid of Google Earth, one can go to:
GISS Surface Temperature Analysis
http://data.giss.nasa.gov/gistemp/station_data/
… click on Greenland then select individual stations — although one should note that some of the stations in that list will be from outside of Greenland as the list is determined by distance.
*
Looking more broadly using available GISS analysis and Sea Surface Temperature records up to the present (with interpolation), one gets a pattern showing less warming in the later part of the twentieth century in Greenland when compared against other land at the same latitude. Not that unexpected. It is an island in the middle of the north Atlantic, afterall. As such, it is strongly affected by the surrounding ocean with its greater thermal inertia, and it should have less amplification than that which one finds on the major continents at the same latitude. Nevertheless, it is a large island, and polar amplification affects the oceans, not just the land. As such it is still warming much more rapidly than lower latitudes.
Please see:
http://data.giss.nasa.gov/cgi-bin/gistemp/do_nmap.py?year_last=2007&month_last=12&sat=4&sst=1&type=anoms&mean_gen=0112&year1=2007&year2=2007&base1=1951&base2=1980&radius=1200&pol=reg
… for an example of an anomaly map for 2007 using GISS analysis for land, Hadl/Reyn_v2 for ocean, mapping anomalies, for annual temperatures, standard base period of 1951-1980, and standard smoothing radius of 1200 km.
Howver, to create your own map, please go to:
http://data.giss.nasa.gov/gistemp/maps/
*
Satellite Records
To get a good satellite image of global temperature anomaly trends for the lower troposphere from 1979-2007 using RSS (which has not been subject to the severe errors of Christy’s UAH), check:
http://www.ssmi.com/msu/msu_data_description.html#msu_decadal_trends
Greenland is a little difficult to see from this perspective, but it is clearly experiencing much the same polar amplification as the rest of the world at that latitude. Note that at the right you will see a good diagram showing the warming by latitude. Likewise, the northern hemisphere is warming more rapidly than the southern. However, for a brief detoir to Anatarctica which also appears in the same image, keep in mind the fact that this is lower troposphere. As such, it shows cooling the closer one gets to the south pole, and nearly none of the warming which is taking place in the Southern Ocean or along the West Antarctic Peninsula.
There is of course considerable cooling still taking place in Antarctica. This would appear to be in large part due to its isolation from the rest of the world as a result of the circumpolar current and enhanced downward atmospheric polar vortex, and the strong interaction of the troposphere, the stratosphere, the polar vortex and the Transantarctic mountains. In accordance with predictions for an enhanced greenhouse effect, the stratosphere has been experiencing cooling as the result of increased levels of carbon dioxide and water vapor which cool the stratosphere as they are radiating above the effective radiating layer where thermal radiation tends to escape to space. Likewise, there has been some cooling of the stratosphere due to decreased levels of ultraviolet-absorbing ozone that would otherwise warm the stratosphere by absorbing energy directly from sunlight. Likewise, given its isolation from other continents, we have long expected polar amplification to become dominant across the antarctic much later than in the northern hemisphere.
However, while temperatures are dropping in much of the Antarctic (at least from 1982-2004 — much of the modern era of global warming), sea surface temperatures are rising along nearly the entire coast — consistent with polar amplification. Thus while the warming around the West Antarctic Peninsula barely shows in the above map, in fact parts of the West Antarctic Peninsula have temperatures that are rising more quickly than anywhere else in the world and nearly the entire coast is warming, with much of it warming more quickly than anywhere else in the ocean south of the equator.
Please see:
Antarctic Temperature Trend 1982-2004
http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17257
… which contains a lovely map based upon skin temperature - the temperature of the layer of the atmosphere which is in contact with the surface, whether it is land or ocean. This map is one of the NOAA products made possible by AVHRR, the Advanced Very High Resolution Radiometer.
For more on the instrument, please see:
Advanced Very High Resolution Radiometer - AVHRR
http://noaasis.noaa.gov/NOAASIS/ml/avhrr.html
For more data imaging products from the use of AVHRR, please see:
Goddard Space Flight Center, Scientific Visualization Studio: Table of Contents for AVHRR
http://svs.gsfc.nasa.gov/search/Instrument/AVHRR.html
… and for other instruments and their data imaging products, please see:
Scientific Visualization Studio
http://svs.gsfc.nasa.gov/search/Instrument/index.html
… for another one of my favorite instruments, please see:
AIRS - Multimedia
http://airs.jpl.nasa.gov/Multimedia
Hank Roberts // January 14, 2008 at 5:44 am
Search Scholar for
mercury greenland sources coal
E.g.
Determination of Mercury Content in a Shallow Firn Core from Greenland by Isotope Dilution
JL Mann, SE Long, CA Shuman, WR Kelly -
Water, Air, & Soil Pollution, 2005 - Springer
… The main sources of anthropogenic Hg to the Arctic are from Eurasia and North America …
Individual coal beds have characteristic isotopes of many metals that can be traced downwind from their sources in this way.
Barton Paul Levenson // January 14, 2008 at 12:50 pm
John Finn posts, again:
[[Industrial aersosols are an unkown fudge factor. ]]
Your posting this again when it has been clearly explained to you in several ways why it’s wrong shows that you’re being intellectually dishonest. It looks like you’re just determined to keep repeating “fudge factor, fudge factor,” no matter what anybody else says. Troll!
John Finn // January 14, 2008 at 2:54 pm
[Your posting this again when it has been clearly explained to you in several ways why it’s wrong shows that you’re being intellectually dishonest. It looks like you’re just determined to keep repeating “fudge factor, fudge factor,” no matter what anybody else says. Troll! ]
BPL they are A) unknown - because nobody can quantify their effect and also B) A fudge factor because they are used to expalin mid 20th c cooling without justuification
OK one last go!
In an earlier post I wrote
[[Aerosols are a fudge factor. If they were the real reason for cooling it would be easy enough to demonstrate it. ]]
I should probably have said “show” rather than “demonstrate”. What I meant was show (or demonstrate) that the mid 20th century cooling was due to industrial aerosols (not as BPL has done and demonstrated the effect of stratospheric aerosols). By showing the industrial effect I mean showing that the greatest cooling is (or was) ‘centered’ on the regions of highest industrial activity. Aerosols don’t remain in the atmosphere long enough to become “well-mixed”, so although there may be some dispersal the greatest effect will be local to the source.
Greenland cooling is unlikely to be due to reflective aerosols since A) the cooling is greater than many industrialized regions; B) there simply wouldn’t be sufficient aerosols to have any effect (most get rained out before they get too far) and C) a large part of Greenland’s surface reflects solar energy anyway.
I do have a question for BPL, though. How much of the industrial-produced aerosols actually make it up into the stratosphere? Not a lot, I would imagine. I know that stratospheric aerosols cause cooling but they are normally the result of volcanic eruptions, e.g. Pinatubo where the volume of ejecta is on a different scale altogether and the dust/ash does actually encircle the earth.
TC: estimates from “industrial output, air samples and ice core” tells us nothing about the radiative effects of the aerosols. But don’t take my word any of this, just check out the paper “Climate Over Past Millenia” by your good friends Michael Mann and Phil Jones, In Section 5.1.4, they say
[ Compared to greenhouse gas forcing, sulphate aerosol forcing is far more uncertain, principally because of the limited understanding of the radiative properties of the aerosols and their effect on clouds. This forcing is also REGIONALLY SPECIFIC and must be estimated from past fossil fuel use ….]
We’ll ignore the “uncertain” bit for now, though it is an issue. Let’s concentrate instead on the last sentence, i.e. “This [aerosol] forcing is regionally specific…” which is then followed by “… and must be estimated from past fossil fuel use”.
I would have thought that one good way of validating the “estimate” of regional aerosol forcing (from past fossil fuel use) is to check out the temperature changes on the regions in question thereby removing some of the aforementioned uncertainty – which @ 1 w/m2 is almost as much the estimated 1.6. w/m2 due to increased CO2 concentrations.
The fact that considerable uncertainty still exists (see IPCC estimates of forcing) tells us all we need to know.
Right, BPL - Now show us the radiative effects of aerosols (with validation).
dhogaza // January 14, 2008 at 7:36 pm
It appears to me that John Finn is ignoring every said by Timothy Chase above.
Barton Paul Levenson // January 14, 2008 at 8:54 pm
Sorry, Finn, you are just assuming counterfactual positions and then refusing to budge (e.g. “no one can quantify their effect,” when several studies have made quantitative estimates). You can’t teach someone who doesn’t want to be taught. There’s enough information here for someone who’s really interested in the science to learn a bit and to check out more. That doesn’t seem to include you.
cce // January 14, 2008 at 11:32 pm
Sulfur in the greenland ice sheet, 1880 to 2000
http://www.giss.nasa.gov/research/features/temptracker/greenland_sulfur_532.gif
You can see from the spike in sulfur around 1991 the relationship of Pinatubo to anthropogenic emissions.
I’m no expert, but the direct effect of SO2 would reflect sunlight regardless of whether it is in the troposphere or the stratosphere. The indirect effect (cloud enhancement) would happen only in the troposphere. But I’m no expert.
Now, looking at tamino’s plot of Greenland temperatures, http://tamino.files.wordpress.com/2007/10/greenlan.jpg
It’s hard to tell because the data is so heavily smoothed, but it sure looks like temperature and sulfur are negatively correlated.
Greenland is also highly sensitive to whatever the North Atlantic Oscillation is doing. The temperature seems to be correlated to the NAO index, although according to several descriptions, it is supposed to be negatively correlated (maybe it’s only the winters that are supposed to be colder).
http://www.ldeo.columbia.edu/res/pi/NAO/
Timothy Chase // January 14, 2008 at 11:53 pm
Aerosols and Models
Previously I had gone into the temperature record for Greenland and to some extent Antarctica. In fact, I barely touched on aerosols and their cooling (or for that matter, warming) effects — which will of course be dependent upon their atmospheric distribution.
I. Aerosol Distribution
Given the importance of their distribution, we should look at how well-distributed they get.
Here is a nice place to begin — with satellite images and animations thanks to NASA — which show aerosol optical depth, both as measured by MODIS and as modeled by GOCART:
NASA Scientists Use Satellites to Distinguish Human Pollution from Other Atmospheric Particles
NASA’S Earth Observatory, RELEASE NO: 02-137
September 17, 2002
http://earthobservatory.nasa.gov/Newsroom/Aerosols/
Now the first point to keep in mind when looking at this is that what we are seeing is limited in two fairly crucial respects. First, they have difficulty picking up aerosols over land. And second, they cannot pick up aerosols in clouds — at least not using this particular technology. The second of these is particularly important when it comes to the indirect effects of aerosols. We aren’t going to see the indirect effects here — but the indirect effects of aerosols where aerosols act as the nuclei for cloud-formation. Clouds warm and cool — with cloud greenhouse effects due to cloud absorption and emission of longwave radiation and cloud albedo effects due to clouds reflecting shortwave radiation. And a great deal of literature is being devoted to trying to discern the indirect effects of aerosols which result from their inducing cloud formation. But we can get into this in more detail shortly.
Before looking into the indirect effects, let’s look more closely at the distribution of aerosols — at least where we can see them in the satellite images given above. You will notice that they extend well into the oceans, far away from the coasts — often passing over the entire width of the Atlantic, across the Pacific, down around the coasts of Antarctica, and at least as modeled (since these particular images don’t reach above a certain latitude), above the Arctic Circle in concentrations sufficient to achieve considerable optical depth. Likewise, while the matchup between the motion satellite images and GOCART modeling aren’t perfect (how could they be — as small variations in initial conditions will result in different runs?), but when comparing the results from both by viewing the movies you can see that they are a rather good match. This in itself suggests that the modeling of aerosol distributions is performing quite well.
Aerosols are known to have substantial direct effects which go well beyond a merely local scale. For example, warming direct effects have been implicated in changes to the Indian Monsoon:
Lau, K. M., Maeng-Ki Kim , and Kyu-Myong Kim (2006): Asian summer monsoon anomalies induced by aerosol direct forcing: the role of the Tibetan Plateau. Clim. Dyn., 26, 7-8, 855 - 864
Abstract: http://www.springerlink.com/content/6889532173180j83
Likewise, natural dust coming off of the Sahara have been implicated in reduced hurricane season for 2006:
An edited version of: Lau, K.-M., and K.-M. Kim (2007), How nature foiled the 2006 hurricane forecasts, Eos Trans. AGU, 88, No. 9, 27 February, 2007
http://atmospheres.gsfc.nasa.gov/publications/2007/EOS_LauKim_2007.htm
As such, it would seem to have a significant impact upon climate — even when considering only the direct effects.
II. Post-WWII Cooling
However, as I have suggested, the strongest effects of aerosols would appear to be their indirect effects through cloud-formation. Some indication of their importance in this area is suggested by the phenomena of solar dimming and at least apparent solar brightening. I will bet getting into that shortly. However, as we are interested in the era of post-WWII aerosol cooling, it might be worthwhile to briefly look into forcings and modeling.
Now in terms of IPCC best estimates, the current direct and indirect effects of aerosols do not add up to that of carbon dioxide. Nevertheless, there is still a great deal of uncertainty regarding these two components, particularly the larger indirect effect. However, even assuming the upperbound of both at a combined -2.7 W/m^2, this does not add up to enough to cancel the best estimate of the net effect of anthropogenic greenhouse gases at 2.94 W/m^2.
Please see:
Aerosols: The Last Frontier?
http://www.realclimate.org/index.php/archives/2007/02/aerosols-the-last-frontier/
… but this is a recent development, one belonging to the modern (late 1970s to present) era. Looking at NASA best estimates, while the forcing due to methane and carbon dioxide exceeded that of the sun ever since 1881 relative to a base year of 1880, carbon dioxide by itself was much less of a force in the early part of the twentieth century. In fact, NASA shows a peak in net forcing for the year 1941 of 0.3066 which is not exceeded until 1945 at 0.3127 and then another peak in 1948 at 0.3951 which is not exceeded until 1956 at 0.4356 — with the quantities of emissions and forcing due to solar irradiance being estimated independently of the general climate model itself.
Please see:
Forcings in GISS Climate Model
http://data.giss.nasa.gov/modelforce
(Note: the charts have been updated to a base year of 1750 to be consistent with IPCC analysis)
… and for the estimates of the quantities of emissions, etc., please see the links in section “Further Details and Various Future Scenarios to 2100″ of the above page.
For the NASA GISS estimated forcings for each year, please see:
Global Mean Effective Forcing (W/m2)
http://data.giss.nasa.gov/modelforce/RadF.txt
(Note: the estimated forcings have yet to be updated from the base year of 1880 to 1750, but the estimates of the physical quantities remain the same)
… and for the results of these forcings with the most recent GISS model, please see:
J. Hansen et al. 2007, Climate simulations for 1880-2003 with GISS modelE, Clim. Dynam., 29, 661-696, doi:10.1007/s00382-007-0255-8.
http://pubs.giss.nasa.gov/abstracts/2007/Hansen_etal_3.html
III. Forcings and Simulations
In terms of the annual effect upon temperature of net forcing, what will be most important is not the the net forcing itself (which is most important in terms of final equilibrium) — but the rate of change in net forcing. Thus one is able to get an impression of how well the cooling period from 1945-1951 is handled by the most recent GISS modelE by looking at page 665 of the above paper. It shows precisely the sort of “dip” that one would expect — given the trend in temperature for that period.
However, there are fairly significant deficiencies in the model runs. For example, a 25% deficiency in summer stratus cloud cover off west coasts of continents, a deficiency in absorbed and net radiation in the tropics typically by 20 W/m^2, a deficiency in cloud cover over the United States and Asia resulting in excessive temperatures during the summer, etc.. See pg. 665. The modelers are quite up front about the actual problems with the model. Including the physics which they are still missing, such as gravity-wave drag on the upper atmosphere — which may correct some of these issues.
But I would strongly recommend checking the results of their calculations for Lower Stratosphere Temperature Anomaly, Surface Temperature Anomaly, Net Radiation TOA, Middle Troposphere Temperature Anomaly, and Ocean Ice Cover (%) on page 672, as well as temperature anomaly maps beginning on page 678 where one should compare Observations (row 1) against All Forcings (row 2).
IV. Regarding the Nature of Modeling
The match on many of the measures is impressive, particularly once one keeps in mind the fact that the curve that results for any given modeled variable is intimately connected to others by means of the same physical laws embodied in the model and constant parameterizations of surfaces and flux exchange between neighboring grid cells. Parameterizations are the one sense in which one may reasonably claim that climate models are an instance of curve-fitting. However, parameterizations are required since any representation of physical laws in terms of finite difference mathematics must cannot itself be modeled below the subgrid level — except by means of parameterization. And they are a localized form of curve-fitting where the same constant set of equations determine the exchange of fluxes (momentum, heat, mass, energy, etc.) between neighboring cells and same constants for each category of surface and the like get applied throughout the tota